Extreme climate change: damage and responsibility

[Making a break from usual topics to repost an essay I just had published in the Australian Quarterly that focuses on some of the implications of my research field]

Climate scientists use the same statistical techniques to determine global warming’s influence in extreme climate events as public health researchers use to investigate the health impacts of smoking and asbestos exposure. The last 31 years have been hotter than average, culminating in a recent increase in the frequency and severity of extreme climate events. The future will serve up more extremes. Public health parallels raise the question, who is responsible for future damages from climate change?

As early as February 2016, climate scientists were making evidence-based predictions that 2016 would become the hottest year in the observational record. Their predictions played out with dire consequences. An aerial survey of the Great Barrier Reef in April 2016 estimated that over 90% of the coral had experienced bleaching. A rapid response scientific analysis determined that the catastrophic die back event would not have been possible without climate change increasing sea surface temperatures that are strongly associated with bleaching.

For Australia, this was just one element of a period of persistent heat. Following the comparatively cool and wet years of 2010 and 2011 when Australia was under the influence of a La Niña episode, an unprecedented period heat began. During this extreme period, hundreds of Australian temperature records were broken. In 2013 alone, Australia experienced its hottest day, week, month, season and year on record. The Bureau of Meteorology added additional colours to a January weather forecast to accommodate the never before recorded extreme temperatures expected for the following days. Some of these records were broken again in 2014, and again in 2015. The unprecedented heat has not yet abated.

This catalogue of record-breaking temperatures constitutes far more than a note in the margin of Australia’s climate history. These years of excess heat have been accompanied by severe impacts that relentlessly affected Australian communities and our natural environment. 2013 began with bushfires across Tasmania’s southeast, which were followed by unseasonably early bushfires in the Blue Mountains in Spring 2013. Heatwaves in January 2014 shut down play at the Australian Open, while literally thousands of fires were reported in a 24-hour period. As heatwaves impacted human health and our built environment, unequalled marine heatwaves impacted coastal ecosystems.

Recent Australian extremes are one part of a longer trend of unusual heat occurring right across the globe. As I write this in late 2016, I am 33 years old, having lived the last 31 years in a world where average monthly temperatures worldwide have been warmer than the average for the twentieth century. That’s 372 consecutive months. I am no longer young but have no memories of a “normal year.” My partner, now 28 years old, has not been alive in a “normal year.” I’ve never seen the Great Barrier Reef and I probably never will. At best, I might see the impoverished, bleached remains of a previously great wonder of our natural world.

Recent record-breaking temperatures are a clear prelude to future climate change. I am at the age where many friends have young children, and are filled with the typical anxieties about providing them with the best start in life. The future lives of these children lies firmly in a world where our recent shattering temperatures will be mild. While I grew up in a world above average, our children’s world will be extreme. The scientific evidence is clear, with a suite of scientific studies comprehensively linking the occurrence of Australia’s recent record-breaking weather to human-caused climate change. In mid-2013, I published a paper with my University of Melbourne colleague Professor David Karoly that demonstrated Australia’s summer of 2012/2013 – the hottest on record – was five times more likely because of anthropogenic climate change. Two separate analyses further revealed that the record-breaking temperatures experienced in Australia in 2013 – the hottest in the Bureau of Meteorology’s records extending back over 100 years – were virtually impossible without the influence of anthropogenic greenhouse gases.

The extreme event attribution technique used for these studies was pioneered well over a decade ago. Dr Peter Stott of the UK Met Office led a study investigating the specific causes of Europe’s 2003 summer heatwaves, which resulted in over 14,000 heat-related deaths across Europe. Greenhouse gas warming had doubled the risk of Europe’s extreme temperatures. Stott’s attribution approach – termed ‘fraction of attributable risk’ (FAR) – was co-opted from the public health sciences, where it is used to provide quantitative insights into the contribution of a risk factor to a disease outcome. In this context the FAR approach asks, how does smoking change the likelihood of developing lung cancer?

Fraction of attributable risk puts a number value on the influence that a particular factor (e.g., smoking or carbon dioxide) had on a particular event (e.g., lung cancer or a heatwave, respectively). For climate extremes, identifying and quantifying contributing factors requires the use of computer climate models to calculate event probabilities. While the type of models varies between different studies, there are commonalities in event attribution approaches. In my study of the Australian record hot 2013 summer, we calculated the probability of hot summers in two different climate model experiments. In the first instance, the frequency of extreme summers was calculated in climate models where both human-caused (changes in greenhouse gases, aerosols and ozone) and natural (solar radiation changes and volcanic) climate factors were included. The second model experiment represents a “world that might have been” without industrialisation, and includes only natural climate factors. In this way, natural and human climate influences can be separated, and as with disease and risk factors, the role of a specific factor in a specific outcome can be quantified.

The parallels between epidemiology and climate science can readily be extended into policy and regulation. The established link between lung cancer and smoking has long had implications for the tobacco industry and its regulation. Similarly, the link between mesothelioma and asbestos restricts the activities of industrial building companies. What about implications for our social, political and economic landscape of the established links between anthropogenic climate change and high-impact extreme weather and climate events? Who is responsible for the future damages of extreme climate events? Prior to the more “extreme” extreme heat of 2016, 2015 was the hottest year ever recorded for global average temperatures. For a climate scientist it is a trivial task to take existing data from climate model projections and explore 2015 temperatures in future scenarios. While 2015 temperatures were alarming at the time, such temperatures are projected to be cooler than average temperatures by 2040 at the latest. Who is responsible for the impacts of such extremes?

Oxford University climate scientist Professor Myles Allen first framed discussion of the climate extremes in terms of liability. Writing on climate liability in 2003 as flood waters burst from the river Thames, Allen argued that the issue of attribution was penetrating as “it touches on a question that is far closer to many of our hearts than global sustainability or planetary survival – who to sue when the house price falls?” While Allen’s seminal discussion raised the possibility of increased insurance premiums and depressed housing markets, there are alluring possibilities for broadening approaches and exploring liability for damage more directly. Increasingly sophisticated techniques and enhanced computational capacity allow a greater range of events – heatwaves, floods, drought, heat deaths, coral reef bleaching – to be analysed for a human fingerprint with ever greater levels of certainty than Allen’s exploratory possibilities. A recent study, for example, showed that climate change increased the risk of heat-related mortality in Paris, one of the worst affected cities in the 2003 extreme heat, by about 70%. The scientific capacity to explore the human influences on the tragic 2009 Black Saturday bushfires is imminent. If such a study reveals that the Black Saturday tragedy was aggravated by climate change, who is responsible for avoiding future damages?

The parallels between disease outcomes and climate impacts are, of course, imperfect. One research avenue focuses on the outcomes of an individual using a population cohort, the other on the impacts of capricious and dynamic environmental systems. Regardless, both applications explore the outcomes of complex, multi-factorial systems in terms of quantitative changes in risks and likelihoods using overlapping statistical techniques. If such a technique is appropriate for instigating regulatory overhaul in one sector (as in the tobacco industry), a durable argument can be made for its applicability elsewhere. That is, scientific event attribution should therefore impel recognition of responsibility for future climate impacts.

Climate scientists have long urged decisive action on climate change. When commenting on another climate record smashed, or more likely smashed again, we aim to communicate clearly the grave risks of climate change, without erasing all hope of meeting such expansive challenges. The seriousness of Australia’s recent extremes cannot be overstated, but such threats are alarming at best, terrifying at worst. When discussing my scientific results, I strive for clear, urgent and hopeful missives to the public and our policymakers. However, as climate scientists issue warnings about the severity of unseasonable bushfires, other key public voices actively undermine this message.

After the unseasonably early Blue Mountains bushfires in spring 2013, then Prime Minister Tony Abbott rejected their presence as a diagnostic of human influences on the climate system. During the record-breaking spring temperatures in Australia in 2013, Abbott said “… the thing is that at some point in the future, every record will be broken, but that doesn’t prove anything about climate change. It just proves that the longer the period of time, the more possibility of extreme events.” Intuitively, Abbott’s statement seems reasonable, but such rhetoric is easily refuted by readily available scientific data and simple statistical analyses. Indeed, Abbott’s Environment Minister, Greg Hunt, disregarded a ministerial briefing from the Australian Bureau of Meteorology and turned to Wikipedia for scientific advice, agreeing that no individual event can be linked to climate change.

These political voices are powerful. Willfully disregarding scientific evidence about the impact of climate change undermines scientific authority and polarises public understandings. As a result, we collectively prevaricate and we negate our ability to avoid future climatic change. Long-lived greenhouse gases, such as carbon dioxide and methane are chemically stable and persist in the atmosphere for decades, centuries or longer. This means that carbon dioxide emissions from today’s industrial processes, transportation or power generation, will impact for the atmosphere, and hence the climate, for decades to come. This perturbation in the climate systems is “locked in” by today’s decisions. The erosion of scientific credibility by our current cohort of politicians impacts the climate our children – the children of politicians and scientists alike – experience in a very direct sense.

I have used the word responsibility with purpose. Framing the impacts of human-caused climate change in terms of ‘blame’ is limiting. Blame is divisive and difficult to attribute. Climate change is an issue of scale and complexity that is near impossible to conceptualise. It affects everyone for decades past and for decades to come. It takes in all elements of the physical and human world and exploits all manner of inter- and intra-generational tensions. Sadly, I epitomise the problem. As an unremarkable white, middle-class Australian, I aspire to an ordinary life of a solid job, secure housing, a family of my own and occasional holidays. Such everyday aspirations and routines choices are the very essence of the climate change problem. Ordinary people living ordinary Australian lives remain antithetical to aggressive climate action.

While my personal contributions to a warmer future cannot be readily circumvented while aspiring to an ordinary life, the contributions from our political leaders are actively harmful. I argue that Tony Abbott’s archive of statements that climate change is absolute crap or complete hogwash carries greater responsibility for future climate impacts than my occasional but unnecessary drive to the local shops. His statements impact public perceptions, flow through to policymaking and crumble international momentum for change.

This understanding of responsibility for future climate damages might seem overly simplistic. Political capacity to respond to the causes and impacts of global warming coalesces in a complex cultural and economic environment that encompasses a suite of tensions on all temporal and spatial scales. Other approaches have focused instead on corporate responsibility for greenhouse gas emissions, with a 2013 study employing a carbon accounting approach to hold some 90 companies responsible for climate change. However, this apportioning of responsibility negates the choices made by individuals and government, who also benefit from the industry of these 90 companies. Further responsibility for obfuscation on climate action can be placed on a multitude of mechanisms extending vastly beyond any individual, from the media to tensions between democracy, consumerism and globalisation.

These intricacies do not entirely negate political responsibility or power. While Australia has long been bound in a Sisyphean approach to climate change that has scarcely shifted since Kevin Rudd’s 2007 proclamation of the greatest moral challenge of our generation, other countries have acted. In 2015, the Climate Change Performance Index ranked Australia last of OECD countries. Even within Australia, while successive federal governments remain mired, various states and territories have implemented far more ambitious greenhouse gas emissions reduction targets, including for example, net zero emissions from Victoria and the ACT by 2050. These efforts align with commitments made across the OECD, but have been impeded and criticised by Prime Minister Malcolm Turnbull as unrealistic. Following the phenomenal storms in South Australia in late September 2016, Turnbull and his various ministers linked widespread power outages to a reliance on renewable energy sources, although scientific experts comprehensively rejected any such assertion.

Returning to parallels with public health risks and regulation, politicians should not be viewed as personally responsible for our children’s climate future. Instead, we can regard Malcolm Turnbull, Tony Abbott and Greg Hunt as we would pro-tobacco advocates, who actively discredited science, spread confusion and disseminated false information. The doubt perpetuated by Turnbull and ministers following the September 2016 storms has the capacity to influence widely, from public opinion, to our energy landscape and our future climates. While in the public health realm, Australia’s political decisiveness has led the world on regulating the tobacco industry and minimising health risks, in regards to climate change, political influence has created doubt that likely enhances the risks of future extremes.

I agonise over my desire for children of my own. In my scientific work, I have already glimpsed their extreme future – their health, environment and livelihoods will be diminished by my own ordinary life. Sadly, their climate challenges are only footnotes in climate impacts. Australian communities have the wealth and capacity to adapt to impending change and mitigate the severity of impacts. Such responses are not available to low lying Pacific Island nations, already being engulfed by our rising seas. While we obfuscate on anthropogenic climate change and baulk at the cost of acting, entire countries and cultures are at stake. Although responsibility for climate change crosscuts time and space, the role of Australia’s recent and current leaders in greeting our future, warmer world cannot and should not be negated. We need political leaders to look beyond their short-terms interests, factions and election cycles to our children’s extreme future. This is the very duty we have elected our leaders to shoulder with due responsibility.